In general, in a static operation, connectors coupled with each other are fastened by a friction therebetween and thereby prevented from looseness. Under a dynamic operation or a frequently vibrating operation, it is not enough to prevent the connectors coupled with each other from looseness by only the friction therebetween. Therefore, a nut and a thread are commonly used for screwing the connectors to further avoid looseness.
However, in certain operation, relative rotation between the two connectors might be required, or extremely frequent vibrations occur, those may gradually cause relatively rotational looseness between the nut and thread.
In views of this, in order to solve the above disadvantage, the present inventor studied related technology and provided a reasonable and effective solution in the present disclosure.